Centrifugal casting



specific heat of 0.10, w ich A tantra LEQN GAMMEN, 0E NEW YQM, N. Y.

7' CENTRIFUGAJL CASTING.

1 All 0,885.

Ito Drawing.

To all whom it may concern:

Be it known that 1, Leon CAMMEN, a citizen of the United States, and resident of borough of Manhattan in the city, county, and State of New YOIli, have invented certain useful and new Improvements in Centrifugal Castings, of which the following is a specification. v

The present invention refers to the production of centrifugal castings from metals which chill rapidly from the molten-state, a e. g. monel metal or high-chromium steel.

In the past (with the exception of the practice of the present inventor) the molds 1n centrifugal casting were used either at room temperature or warmed up onl sli htly, enough to take of? the chill of the mo d and to ensureits being dry. In fact the present inventor knows of nocase Where the mold was heated higher than 300 to 400 deg. F. As a result of this, it has not proved hitherto possible to produce good and sound centrifugal castings of such metals as monel in tubes of small diameters, such as 3 to 4' in, which I have done successfully by my method. 1

A. brief thermodynamic calculation will show the reasons for the failure to do so. Assume that it is desired to cast a tube in. long, 3 in. outside and 2.5 in. inside diameter. Such a tube in monel metal weighs roughly 60 1b. If before casting the metal is heated to a temperature say 200 deg'. above the melting point (and is not safe to go beyond that the metal will contain roughly (specific heat of monel metal 0.12) 1500 B. t. u. of heat that it, can lose before it reaches the temperature of initial congelation.

But the mold, made up of a refractory material and some metal like steel, must be at least 1.5 in. thick, which means that it will have a volume of at least 600 cu. in. and a combined weight of about 120 to 150 lb. Assuming the lower it re, and a combined is certainly low, one can easil see that it while the metal is being poure the average tem erature of the mold is raised more than 125 eg., enough heat is abstracted to congeal the metal.

From this it clearly appears that, unless the metal is poured so ra idly that it will assume a form of a tube no to centrifugal spinning before the mold is heated up to 125 deg. F. above its lnitial temperature, it

Specification of Letters Patent. Patented'lllllatr. 2d, 1922. Application med- August 112, 1921. Serial Ito. M1345.

is impossible to cast a good tube of the dimensions indicated above; As hitherto no way has been discovered to pour the metal with the rapidity required, and as with the usual methods of pouringand a mold at room temperature, the temperature of the mold during pouring rises several hundred degrees, it has proved to be impossible to ma re small tubing of such metals as monel in cold molds.

The same calculation explains why heating the mold to say 300 or 400 deg. F., as is frequently done now, is of no avail in this connection. As monel metal is being' poured into the mold at say 2700 deg. F., the difierence between aninitial temperature of the mold of say 100 and 400 terial, the rise of temperature of the mold being of the order of 700 to 1000 deg. F., i. e. considerably beyond the limits which are safe if it is desired to maintain the metal after pouring in a fluid condition long enough to permit it to form a good tube.

In this connection it should be mentioned that it is b no means suflicient to maintain the metal uid lon enough for it to acquire a tubular shape be ore it solidifies. in centrifugal casting the ventin of the mold is naturally very poor, and-t e only way the gases in the metal have for their escape is towards the center of the mold, or tube, this being materially assisted by the tendency of the metal to pack ti ht under the action of centrifugal force. ut the only way the gases can thus escape is providing the metal remains fluid long enough. to permit them to do so. If therefore the metal con eals too rapidly, there may be a tubular s ape cast, but the metal will be full of blowholes and porosity.

To-avoid this, the present inventor resorts to a heating of the mold to a ver high temperature, in excess of 1000 deg. and preferably to about 2000 deg. F. for monel metaland steel, and in general, preferably toa temperature not less than one half the melting temperature of the metal to be cast, as expressed in degree of the Fahrenheit thermometric scale, so that e. g. for bronze, melting at 1700 de F., the heating of the mold to say 850 eg. would be suflicient, though the employment of a somewhat higher temperature, sa 1000 deg. F. is recommended.

This heating may be done in various ways, I

deg. is scarcely ma as placing the mold into a furnace, passing an electric current through the mold, etc.

I claim:

1. A rocess of centrifugal casting wherein, prev1ous to the pouring of the metal, the mold is by external means other than the metal of the castinghheatedto a temperature,

in degrees Fahren eit scale, not less than one-half that of the melting'point of the pouring of the metal, is by external means other than the metal of the casting heated to a temperature not less than 850 deg. F.

, 4. A process of centrifugal casting where-- in, previous to the pouring of the metal, the

mold is by'external means other than the metal of the casting heated to such a temperature thatthe loss of heat from the metal to the mold. at its obtaining temperature be less than that which is suflicient to chill the metal to the point of congelation within the time period necessary for the for.-

mation of the proper casting shape and for theescape of the gases from the metal.

5. A rocess of centrifugal casting where- )in, revious to the pouring of the metal, the

m0 d metal of the casting heated to such a temperis by external means other than the ature that the loss of heat from the metal to the mold at its obtaining temperature be less than that which is sufficient to chill the metal to the point of congelation within the time period necessary'for the formation of the proper casting shape.

igned in New York, in the county and State of New York, Au ust 10th, A. D. 1921.

fiEON CAMMEN. Witness:

Louisa 'RnINsoHMnYr. 

